Hydraulic expansion devices, which have a wheel brake cylinder which is connected via a hydraulic line to a brake pressure generator, e.g. to a pedal-operated brake master cylinder, are known.
Electromechanical expansion devices, such as an electric motor-driven cam which is located at the position of the wheel brake cylinder, have already been proposed, especially for electric vehicles.
For operating disk brakes, provision has also already been made for roll ramps in which balls on ramp-like ball tracks are provided between two bodies. By rotation of the one body the balls run up the ramps and in the process force apart the two bodies, which leads to operation of the brake.
In the case of expansion devices for drum brakes, there is particularly the problem that these are provided with a readjustment device which ensures that the air gap between the brake shoes and the brake drum of a drum brake is readjusted incrementally.
The stroke, which an expansion device of the above-described type can provide, is not sufficient to realize a sufficiently large adjustment range for readjusting the drum brake so that such expansion devices have not yet been used up to now for drum brakes.